This invention relates to a surgical instrument for use in eye surgery and particularly cataract eye surgery.
The natural eye in humans contains a lens which focuses on the retina. Due to disease, naturally occurring processes or mutation, the lens may fail to function properly. For example, the lens, by mutation, may have been eliminated from the eye during its formation. Alternatively, the lens may be clouded at birth or become clouded over time. Clouding of a lens is known as a "cataract" which inhibits the transmission of visual information through the lens to the retina.
In the past, the removal of an impaired natural lens required a large incision into the eye at the junction of the cornea and the sclera. As a result, healing time for the incision was substantial. Since the natural lens was removed, eyeglasses or external contact lenses were employed to help restore vision. With the advent of intraocular lenses, incisions initially were still relatively large and healing time remained substantial. The length of the incision required for cataract removal is larger than that required for intraocular lens implantation.
Recently, significant efforts have been made to reduce the size of the incision and such efforts have been successful in substantially reducing the size of the incision for cataract removal to the order of less than 3 mm.
While there has been much success in reducing the size of an incision for cataract surgery, there are still other problems which remain in connection with this surgery.
The method to remove a cataract through a surgical incision in the eye is known as phacoemulsification. Traditionally, this method has involved using a dual chambered instrument consisting of a hollow ultrasonically vibratable metallic needle surrounded by a tubular member. This instrument was inserted through an incision in the eye and the vibratable metallic needle would vibrate at selected frequencies and minute amplitudes fracturing the cataract which was to be removed and replaced by an intraocular lens. While the tip of the vibratable needle serves to engage and fracture the cataract, a suction force is applied through the needle interior to withdraw the fragmented cataract into the needle and out of the eye. During this process, a fluid is infused into the eye through the tubular member which surrounds the vibratable needle. This tubular member is, not surprisingly, known as an infusion sleeve and, in the past, has been made of either a soft silicone material or a rigid composition, in the latter case either metal or teflon.
The importance of infusing a fluid into the eye during cataract surgery cannot be understated. The fluid infusion serves to maintain the eye in an inflated, pressurized condition during cataract removal. These are, however, several factors which increase the difficulties in maintaining an eye during cataract surgery in an inflated, pressurized condition.
One of the most frequent and constant causes of diminished inflation of an eye during cataract surgery is leakage of fluid from the eye. This leakage normally occurs between the egdes of the incision and the exterior surface of the infusion sleeve and can have extreme and adverse consequences to the person being operated on.
One such adverse consequence is that there is a tendency with the loss of fluid for the eye to deflate during the operation which causes the collapse of certain tissues within the eye upon each other or upon the surgical instrument which extends into the eye. The tissues which are most likely to be damaged from the fluid leakage are the cornea, the iris and the lens capsule, all of which surround the cataract. The natural tendency to counteract this fluid leakage is to increase the amount of fluid flow through the eye so that there is proper inflation of the eye. However, this is not a satisfactory solution to the problem of leakage of fluid from the eye because the greater infusion of fluid flow into the eye, the greater the Reynolds number of the fluid such that the flow becomes rapid and even turbulent, causing damage to the cornea and specifically the fragile cells which line the inside of the cornea.
The fragile cells which line the inside of the cornea are known as corneal endothelium and they cannot be regenerated by the eye or, to put it another way, any damage to these cells cannot be repaired by human regeneration. Damage to the corneal endothelium can cause permanent damage to the cornea, resulting in corneal clouding and decreased vision, all of which may require a corneal transplant. In fact, the most common cause of corneal clouding and of corneal transplantation in the United States today are complications from eye surgery during the removal of a cataract and the insertion of an intraocular lens.
It, of course, goes without saying that there would be a tremendous benefit if corneal damage as a result of fluid flow leakage during intraocular surgery could be eliminated.
An early type of infusion sleeve used for intraocular surgery was made of silicone and to this date most of the infusion sleeves used during phacoemulsification are made of silicone or a silicone-type material. However, the use of a silicone-type infusion sleeve presents substantial problems in connection with fluid leakage between the incision edge in the eye and the exterior surface of the silicone infusion sleeve. This results since the incision in the eye must be larger than the silicone infusion sleeve. This is because a silicone infusion sleeve is made from a soft compressible material and cannot be safely used when inserted through an incision in the eye when there is a minimal amount of clearance between the incision and the exterior of the silicone infusion sleeve.
When there is a minimal clearance between the exterior of the silicone infusion sleeve and the incision of the eye, the incision tends to compress the non-rigid silicone sleeve against the vibrating tip which results in relative rubbing movement between the silicone sleeve and the vibrating tip. This relative movement generates undesirable heat as the needle is being vibrated as its relatively high frequencies. The generation of this heat is extremely undesirable inasmuch as it can result in thermal burns and shrinkage of ocular tissue surrounding the silicone compression sleeve. It goes without saying that the burning and shrinkage of ocular tissue is a serious problem and has sight-threatening implications. The rubbing of the infusion sleeve against the vibrating needle also constricts the path for fluid to flow into the eye thereby hampering efforts to keep the eye pressurized and inflated.
In an attempt to reduce the infusion fluid leakage and the deleterious effects that can be caused by undesirable friction generated therefrom, some infusion sleeves have been constructed from rigid non-compressible materials. Generally these materials have consisted of teflon or metallic-based compositions. These rigid, non-compressible infusion sleeves have been relatively successful in solving the problems of constriction of the path for fluid flow between the distal end of the infusion sleeve and the vibrating tip as well as the heat generation and thermal burns associated with malleable infusion sleeves such as the silicone-type sleeve described herein. However, other problems persist with these non-compressible infusion sleeves.
While rigid, non-compressible sleeves are capable of being inserted through smaller incisions which has the inherent advantage of reducing leakage through the clearance between the rigid, non-compressible sleeve and the incision, there is still significant leakage. The primary cause of the persistent leakage between the rigid, non-compressible fluid infusion sleeve and the eye incision is that the cross-section of the rigid, non-compressible sleeve does not match the contour of the eye incision. As a consequence, there are fairly substantial gaps between the rigid, non-compressible sleeve exterior surface and the eye incision. This is because the collagen fiber structure of the cornea resists deformity and thus does not readily assume the shape of the infusion sleeve.
The experience of the applicant, who has performed literally thousands of cataract eye operations, has shown that it is impossible from a practical standpoint to eliminate the problem of leakage during cataract surgery by means of a smaller incision and forcing the infusion sleeve through it. While this may minimize wound leakage, it does not eliminate the problem and in addition causes the instrument to be so tightly held by the deformed incision that there is great difficulty in advancing and withdrawing the instrument through the incision. As will be apparent to those skilled in the art, during cataract surgery the instrument must be advanced and withdrawn many times through the incision as the fractured portions of the cataract are removed from the various locations within the anterior and posterior chambers of the eye.
It is therefore an object of the present invention to provide an improved apparatus for performing cataract surgery.
Still another object of the present invention is to provide an improved surgical instrument for performing cataract surgery which eliminates wound leakage such that it no longer is a practical problem.
Yet a further object of the present invention is to provide a surgical instrument that can be used during cataract surgery for infusing an eye and removing the pieces of a fractured cataract while preventing wound leakage and yet avoid undesirable heat generation heretofore associated with prior art surgical instruments.
A further object of the present invention is to provide an improved surgical instrument that can be used to perform cataract surgery eliminating wound leakage and undesirable heat generation while allowing the vibratable tip to be advanced and withdrawn as is dicated by the necessities of the operation.
The foregoing, as well as other objects, are accomplished by having a surgical instrument which consists of a central vibratable metallic hollow needle surrounded by an infusion sleeve. The infusion sleeve has an ellipsoidal configuration which conforms to the demonstrated configuration of the surgical incision when the incision is opened by the insertion of the instrument. As a consequence of the infusion sleeve matching the configuration of the surgical incision, there is no leakage between the exterior surface of the infusion sleeve and the surgical incision. Still further, the infusion sleeve is normally made of a rigid material such as a metallic material or teflon and thus there is no tendency of the sleeve to collapse and abut against the vibrating metallic needle thereby generating undesirable heat.
As a consequence of the embodiment of the invention just described fluid leakage between the exterior surface of the infusion sleeve and the wound incision is eliminated, providing stable pressure within the eye, eliminating turbulent fluid flow in the eye and correspondingly reducing internal ocular trauma from such turbulent flow. Furthermore, the infusion fluid maintains the ocular tissues in their normal anatomical position preventing collapse thereof either upon themselves or upon the instrument as heretofore occurred.
In a second embodiment of the present invention, an outer silicone infusion sleeve has its distal end tapered so as to be in close proximity to the vibrating needle. Surrounding the vibrating needle is a metallic, non-compressible sleeve which serves the purpose of preventing collapse of the outer silicone infusion sleeve against the vibrating needle. Thus, the outer silicone infusion sleeve will normally assume the shape of the incision (i.e., ellipsoidal) but cannot collapse against the vibrating tip because the metallic infusion prevents this so to preclude the generation of unwanted heat while at the same time eliminating wound leakage.
Other objects of the present invention will be apparent to those having ordinary skill in the art.